The Chicago-born 26-year-old got off to a flying start with four birdies on the first six holes and added two more on the back nine in a flawless opening round at the Carlsbad event.
Australia's Karrie Webb also had six birdies, but blotted her copybook slightly by bogeying the par-four 13th hole and had to settle for a share of second spot alongside Sweden's Caroline Hedwall.
Hedwall had an eventful first day. She was six under through eight holes on her way to an outward 30, but started the back nine with a double-bogey seven at the par-five 10th. She recovered well with a couple of swift birdies before dropping a further shot on 16 to finish on five under.
Italy's Giulia Sergas surged up the leaderboard with three birdies on her final five holes to climb to joint fourth, alongside with Jessica Korda. The American had looked on course to be in an even more promising position but slipped back with bogeys on 15 and 18.
England's Jodi Ewart Shadoff was one of 10 players tied for sixth spot - three shots off the pace on three under - alongside Spain's Beatriz Recari, South Korean trio Inbee Park, Se Ri Pak and Haeji Kang and Americans Paula Creamer, Amanda Blumenherst, Mo Martin, Lizette Salas and Austin Ernst.